ENH: add pytest collector to only select image tests to run

SidharthBansal · tacaswell · commit 2a66ff88dd30 · 2023-06-15T13:56:05.000-04:00
diff --git a/lib/matplotlib/testing/conftest.py b/lib/matplotlib/testing/conftest.py
@@ -15,6 +15,10 @@ def pytest_configure(config):
         ("markers", "backend: Set alternate Matplotlib backend temporarily."),
         ("markers", "baseline_images: Compare output against references."),
         ("markers", "pytz: Tests that require pytz to be installed."),
+        ("markers",
+         ("matplotlib_baseline_image_generation: "
+          "Flag to generate matplotlib baseline images.")
+         ),
         ("filterwarnings", "error"),
         ("filterwarnings",
          "ignore:.*The py23 module has been deprecated:DeprecationWarning"),
@@ -96,3 +100,22 @@ def xr():
     """Fixture to import xarray."""
     xr = pytest.importorskip('xarray')
     return xr
+
+
+def pytest_addoption(parser):
+    parser.addoption(
+        "--matplotlib_baseline_image_generation",
+        action="store_true",
+        default=False,
+        help="run matplotlib baseline image generation tests"
+    )
+
+
+def pytest_collection_modifyitems(config, items):
+    if config.getoption("--matplotlib_baseline_image_generation"):
+        skip_non_matplotlib_baseline_image_generation_tests = pytest.mark.skip(
+            reason="No need to run non image generation tests"
+        )
+        for item in items:
+            if "matplotlib_baseline_image_generation" not in item.keywords:
+                item.add_marker(skip_non_matplotlib_baseline_image_generation_tests)
diff --git a/lib/matplotlib/testing/decorators.py b/lib/matplotlib/testing/decorators.py
@@ -276,6 +276,7 @@ def decorator(func):
         @matplotlib.style.context(style)
         @_checked_on_freetype_version(freetype_version)
         @functools.wraps(func)
+        @pytest.mark.matplotlib_baseline_image_generation
         def wrapper(*args, extension, request, **kwargs):
             __tracebackhide__ = True
             if 'extension' in old_sig.parameters:
@@ -317,7 +318,9 @@ def wrapper(*args, extension, request, **kwargs):
                 f"Test generated {len(figs)} images but there are "
                 f"{len(our_baseline_images)} baseline images")
 
-            generating = bool(os.environ.get("MPLGENERATEBASELINE"))
+            generating = request.config.getoption(
+                "--matplotlib_baseline_image_generation"
+            )
 
             for fig, baseline in zip(figs, our_baseline_images):
                 if generating:
diff --git a/lib/matplotlib/tests/conftest.py b/lib/matplotlib/tests/conftest.py
@@ -1,2 +1,3 @@
 from matplotlib.testing.conftest import (  # noqa
-    mpl_test_settings, pytest_configure, pytest_unconfigure, pd, xr)
+    mpl_test_settings, pytest_configure, pytest_unconfigure, pd, xr,
+    pytest_collection_modifyitems)
diff --git a/lib/matplotlib/tests/test_agg_filter.py b/lib/matplotlib/tests/test_agg_filter.py
@@ -1,5 +1,4 @@
 import numpy as np
-
 import matplotlib.pyplot as plt
 from matplotlib.testing.decorators import image_comparison
 
diff --git a/pytest.ini b/pytest.ini
@@ -10,3 +10,7 @@ minversion = 7.0.0
 testpaths = lib
 python_files = test_*.py
 junit_family = xunit2
+
+
+markers =
+    matplotlib_baseline_image_generation: marks tests as matplotlib_baseline_image_generation (deselect with '-m "not matplotlib_baseline_image_generation"')

Original file line number	Diff line number	Diff line change
`@@ -1,5 +1,4 @@`
`1`	`1`	`import numpy as np`
`2`		`-`
`3`	`2`	`import matplotlib.pyplot as plt`
`4`	`3`	`from matplotlib.testing.decorators import image_comparison`
`5`	`4`